arm64: tegra: Describe Tegra234 CPU hierarchy

The NVIDIA Tegra234 SoC has 3 clusters of 4 Cortex-A78AE CPU cores each,
for a total of 12 CPUs. Each CPU has 64 KiB instruction and data caches
with each cluster having an additional 256 KiB unified L2 cache and a 2
MiB L3 cache.

Signed-off-by: Thierry Reding <treding@nvidia.com>